1. Field of the Invention
This invention relates to an electronic substrate processing system in a clean room, and its equipments.
2. Prior Art
Electronic substrates such as semiconductor wafers are manufactured in a clean room, the atmosphere in which has been cleaned. The manufacture is increased in yield by increasing the cleanliness of the atmosphere.
On the other hand, recently semiconductor integrated circuits have been increased in the degree of integration. In association with this increase, a so-called "local clean system" has been employed in which electronic substrates such as semiconductor wafers are set in a portable closed container when conveyed. For instance in a processing step in which a thin film forming deposition system (CVD, PVD or the like) is carried out for wafers, the degree of growth of a native oxide film on the wafers, or the contamination of the wafers by metal ions contained in the air cannot be neglected; that is, the exposure of the wafers in the air cannot be neglected in manufacture of the wafers.
Prior to the thin film deposition system, the wafer is cleaned with a cleaning equipment. This wafer cleaning operation should be carried out with the thin film deposition system taken into account because the thin film deposition system takes a relatively long period of time, several tens of minutes to several hours, for the following reasons: A native oxide film grows on the cleaned wafer quickly; that is, the cleaned wafer is liable to be contaminated by the ions in the air. Therefore, if, in the thin film deposition system, wafers to be processed next are exposed in the internal atmosphere, then a native oxide film grows on them (the percentage of growth of the native oxide film being increased abruptly in about one hour exposure), and they are progressively contaminated by the metal ions.
Sometimes the cleaning operation by the cleaning equipment takes several tens of minutes. Hence, in the conventional processing system, the processing operation is less in the degree of freedom, and therefore it is difficult to increase the productivity.